The objectives of this study are 1) to investigate magnetic resonance (MR) imaging and positron emission tomography (PET Scans) as a possible tool for quantifying inflammatory synovitis and monitoring changes in disease activity following short-term treatment interventions and 2) to determine whether anti-TNF-` decreases nitric oxide (NO) production in RA. This study was done in conjunction with the ANTI-TNF clinical trial and involved an analysis of NO production and joint imaging in 9 patients with rheumatoid arthritis. Participants were admitted to the Clinical Research Center and fed a low nitrate and nitrite diet for 48 hours. Blood and urine samples, saliva test, and disease activity, MR imaging and PET scan assessments were obtained at baseline and 4 weeks after study drug infusion.. Nine patients completed the baseline and week 4 procedures. Analysis of this study is pending unblinding of treatment assignment. The study is closed.